Catalytic converters are well known for the removal and/or conversion of the harmful components of exhaust gases. For gasoline engines, they typically contain a three-way conversion (TWC) catalyst and are located in the exhaust gas line of internal combustion engines. Such catalysts promote the oxidation by oxygen in the exhaust gas stream of unburned hydrocarbons and carbon monoxide as well as the reduction of nitrogen oxides to nitrogen. For diesel engines, which run under lean operating conditions, a diesel oxidation catalyst (DOC), which promotes oxidation of unburned hydrocarbons and carbon monoxide, is usually provided.
Catalytic converters have a variety of constructions for this purpose. In one form, the converter comprises a rigid skeletal monolithic substrate on which there is a catalytic coating. The monolith has a honeycomb-type structure which has a multiplicity of longitudinal passages, typically in parallel, to provide a catalytically coated body having a high surface area.
Monolithic honeycombs containing different catalyst compositions are disposed in zones along the length of the honeycomb are used in catalytic combustion processes. Layered catalyst structures can be made on ceramic and metallic monolith structures by a variety of processes. Multi-zoned catalyst and trap are provided in U.S. Pat. No. 7,189,376 (Kumar). Automotive hydrocarbon adsorber systems are provided in U.S. Pat. No. 5,916,133 (Buhrmaster).
In exhaust gas lines, limited piping space, for example at an elbow, between the engine and a catalytic converter and lead to mal-distribution of flow through the catalytic converter. This mal-distribution of flow affects catalyst efficiency and conversions during transient conditions.
In order to meet ever more stringent emission standards set by various regulatory agencies, such as the proposed SULEV emissions regulations, there is a benefit to develop catalyst architectures that assist and advance light-off of, for example, three-way conversion catalyst light-off. In addition, it is desirable to refine zone-coating technologies and evaluate placement of particular catalytic or pollutant adsorbent compositions along the catalyst's length and radius.